
function shopping(bring) {
	console.log('shopping begin.')
    if (bring) {
        console.log("来来来，买给你");
        bring();
    }
	
	console.log('shopping done.')
}

function buySomething() {
    console.log("buSomething execute.");
}

shopping(buySomething);
shopping()
// shopping(buySomething());